Three-phase Ac Motor Spwm Frequency Control System Design And Research

An open-loop virable frequency virable speed (VVVF) controlling system is designed in this paper. Basic techniques of VVVF are introduced, such as mechanical characteristics of motor under VVVF control, fundamental theories which Sinusoidal Pulse-Width Modulation (SPWM) control algorithm are based on, and macro computer unit (MCU) realization of SPWN, etc. Software and hardware used in this design are specified, as well as the resulting design of main circuit, protecting circuit and control circuit for the system. Parameter calculations of rectification, filter, inverter, driving circuits of Insulated-Gate Bipolar Transistor (IGBT), and peripheral circuits are discussed in the design of main circuit. Efforts are made to increase system safety, such as designing of a protecting circuit. Design theory and important parameters of the protecting circuit are described. In the control circuit, microcomputer is used for realizing SPWM algorithm. This controller is chosen to provide real time control and a machine-human interface. Electromagnetism Compatibility (EMC) of digital system is also discussed in this paper. A design method of hardware and software, protection circuit and crosstalk reduction is proposed. A reliable system is developed and verified.